The present invention relates to an elastomeric shaft seal and more particularly to a high pressure, low speed, bi-directional elastomeric seal for sealing high pressure conditions on a slowly rotating shaft.
Elastomeric seals of various configurations have been utilized to provide a seal between a rotating shaft and a housing where a pressurized fluid environment is located on one side of the seal and a second fluid is located on the opposite side thereof. In most instances, a lip-type seal is utilized; especially in a high pressure situation such as for a sector seal for the gear shaft of an automobile power steering unit. In many cases of such a high pressure environment, a stack of two or more lip seal members and reinforcing spacers is necessary.
Problems occur in the stacked lip seal arrangements in the simple operation of assembling the seals onto the shaft; for example, the seals may be positioned in the wrong direction or two seals assembled in opposite directions, thus decreasing the efficiency of the seal. Also, when pressure is applied to a lip seal, the pressure acts directly on the lip and forces the lip tight against the shaft. When the pressure is great enough, the seal lip will be deformed and stretched so as to force a greater portion of the lip surface area tightly around the shaft. The torque required to turn the shaft under this high pressure condition becomes excessive and, correspondingly, lip wear increases and rupture of the "flex section" becomes a distinct possibility. The present invention obviates the above described problems.
Among the objects of the present invention is the provision of a resilient seal in the form of a unitary elastomeric plug for the sealing of high pressures exerted thereon where the seal engages a housing bore and a rotating shaft extending therethrough. This seal will replace one or more conventional type lip seals stacked together and thus reduce assembly time and possible assembly errors. Also, the seal will operate with considerably less torque than lip seals used in high pressure applications.
Another object of the present invention is the provision of a resilient seal where the torque exerted by the seal upon increasing pressure acting on one end of the seal is held at a minimum. The seal has an interference fit with the shaft to effect an initial and static seal. One end of the seal either abuts a shoulder or flange formed on the housing or is retained in a metal shell or cup member positioned in the housing, while the opposite end of the seal is provided with an annular groove forming the seal end surface into a pair of concentric lips or rings; one of which engages the housing bore and the other one engages the shaft. As the pressure increases, the annular rings tend to separate in opposite radial directions to effect a tighter seal.
A further object of the present invention is the provision of a resilient seal which will be lubricated by the pressurized fluid to reduce the torque required to rotate the shaft engaged by the seal. The internal diameter of the seal has a sealing surface with alternating annular rings and concave recesses. When the pressure acts on the one end of the seal, the pressure operates in an axial direction to squeeze the seal body axially and compress the body within the limited space between the shaft and the bore without appreciably increasing the torque required to turn the shaft. Fluctuation of pressure against the seal will cause the annular rings to move slightly in the axial direction, which will result in a wiping and distributing action for a thin film of the pressurizing fluid at the interface between the annular rings and the shaft; thus lubricating this interface and further reducing the turning torque requirement of the shaft.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.